Rated 5 out of 5 stars

Από τον/την a-aday στις Σεπτ. 8, 2008 · μόνιμος σύνδεσμος

From an earlier review by DerAlb. Works perfectly by the way:

Download the xpi file, rename it to zip, open it. Then open the included file install.rdf and change the maximum version entry for Firefox to 3.0.something.*.
Overwrite the existing version, rename zip to xpi and install. Worked for me!